fix: Dynamic Power Limiter MQTT topics not carrying the hostname

[AndreasBoehm]

This fixes #963 by including the unique id of a DTU in the topics.

NOTE: This is a breaking change for existing users, as the topics will change.

The changes are based on

OpenDTU-OnBattery/src/MqttHandleHass.cpp

Line 331 in f0df583

void MqttHandleHassClass::publishDtuBinarySensor(const char* name, const char* device_class, const char* category, const char* payload_on, const char* payload_off, const char* subTopic)

[schlimmchen]

As far as I can tell, the "breaking" part of this PR is not too big of a deal. The respective topics are the same, only the entities for HomeAssistant auto discovery change. Does this mean workflows or automation for DPL values break?